...is what happens when a 747 taking off at Gatwick loses an engine. I spent the weekend on the south coast of the UK, and on Satyrday morning was surprised to see a low level 747 with some very odd contrails as I walked into the garden, which a second or three later I figured were a fuel dump in progress - it stopped a minute or so after he'd crossed the coast heading north back to Gatwick.
'So happens some other chap had a camera at the ready, and caught the event HERE!.
Interesting photos, considering most dumps will be done well out to see, and are a fairly rare occurence anyway